makepredictcall
Utility Function for Safe Prediction
Description
A generic function used by model.frame to replace calls
to functions whose default values depend on the first
argument with calls to the same functions with the default
values specified explicitly.
Usage
makepredictcall(var, call)
Arguments
| var |
an object created by evaluating the call argument,
typically a vector or matrix with added attributes.
It is expected that the attributes will contain information
about the values of arguments to the function called by
the call that were not specified in the call.
E.g., the attributes of scale(x, center=TRUE) will
contain the implied numeric values of the for the
center and scale arguments.
|
| call |
the call object from which var was derived (via eval).
|
Details
makepredictcall is a generic function and package writers
are welcome to write methods for it when they write functions
whose default auxillary argument values depend on the main argument.
It dispatches on the class of the object generated by the function
in question and can use language object analysis functions like
formals and match.call on the call to see what actual
arguments were used.
The stats package contains a default method which returns the call,
unaltered, a matrix method which deals with calls to scale,
and a poly method for the poly function.
Value
a call, most of time it is the same as argument call but
for special functions it will have extra or altered arguments so
that calling it with a new value for the main argument will use
the same auxillary argument values as the origanal call.
See Also
Examples
x <- 1:10
makepredictcall(scale(x, center=TRUE), quote(scale(x, center=TRUE)))
# scale(x = x, center = 5.5, scale = 3.02765035409749)